Differences between Mk1,2 and X7 steering racks

[KennyW]

Well you won't believe it I had a look under the sub-frame yesterday dry as a bone, heavens knows whats going on (confused .com). But will be able to look at better today as I've got a sticky f/o/s caliper.

Kenny

[Stickyfinger]

You can only really be sure if you look via the footwell cover (drivers side).....fingers crossed.

[GiveMeABreak]

I do hope that it's not the rack - as that bodes well for the rest of us!

[bobins]

If it's not the rack, it could be the power steering pipes as they like to fail where they plumb into the rack.

[KennyW]

Well looked today and there is small amount of fluid smeared on pinion around the steel plate mounting the pipes.

The best way to describe it has it looks 'damp'.

If I'm going to inspect it properly, I'll have to remove the sub-frame support the rack somehow and check the pinion through the footwell. Check the pipe fitment as well. Much easier to reach the pipes this way.

But, I'm going to leave until better weather arrives !
Since the 'leak' doesn't seem to bad.

Kenny

[GiveMeABreak]

If it is underlying corrosion and the rust has started to distort the seal, I an see this getting worse pretty rapidly, but fingers crossed it may just need a new possibly larger o ring.

[KennyW]

I have tried in the past even on a ramp to replace both seals on the pipes and it is a right faff. Awkward to reach, see and get hands to fit the pipes back on.

Kenny

[bobins]

The design of the 'embossed' ring that is incorporated into the pipe fitment means that the pipes are really only good for single fitment. That ring crushes up against a seat in the pinion housing when the pipe is bolted into position. You might be able to get a satisfactory re-use of the pipe(s) if you could find a way of putting a shim in between the 'embossed' ring and the yoke that clamps the pipe into position, but that shim would have to be sub-1mm thinckness to be workable. Another method would be to shave 0.5mm off the face of the pinion housing where the pipes enter, but to do that satisfactorily you'd need the housing on a bench.

Edited in details from a previous posting I made here:
viewtopic.php?p=590623#p590623

The two options I was playing with was either to fit a ~0.5mm LDS proof ring seal around the pipe at point 'A' where the flange sits on its seat, or to use a ~0.5mm packing piece at point 'B' to enanble the flange to press fully home into its seat. Any more than 0.5mm would probably throw out the how the steel HP pipe seats in its recess.

pipeseal - own work

[KennyW]

Thanks Bobins, your explanation of the crush proportion of the collar makes sense now.

How to replicate that is the question ?

I've been thinking about getting a pipe made up by a hydraulic pipe making company.

I need to find a spare pipe to give them an Idea what is required.

It's almost like the hydraulic pipes fitted to the Xantia where a collar is made by a die.

Kenny

[bobins]

With reference to my photo above - if you could find / make a wafer thin shim that'd sit on the stepped portion of the the pipe hole in the pinion casting, then that would mean you could re-use the old pipe as-is as there'd be a new surface for the ring to crush onto. You'd have to put an identical thickness shim onto the steps in both holes due to the way the pipes clamp into position. I have a pinion casting sitting here in front of me in case you feel the need to get creative and want to go into shim manufacture and need some measurements !

[white exec]

I doubt very much that the swaged flange has any sealing function, except to hold the pipe firmly in position, and prevent any movement. The hydraulic sealing will be solely down to the green O-ring, sitting in the machined bore. This arrangement is pretty similar to the heater matrix pipes on XM/Xantia, which also feature a single O-ring and clamp plate.

PSA are known to be a tad mean on the dimensions of their O-rings (numerous example of this, including those matrix pipes, hydraulic suspension strut tops, and even the sphere 'stoppers'), and increasing the thickness of the O-ring by a small fraction of a mm can improve the seal significantly. Important not to overdo it, and to lubricate the ring (eg silicone grease) when fitting.

I wouldn't be putting any additional O-ring or flexible washer at A, as this would actually encourage movement of the pipe. An extra thin rigid bit of packing at B is a good idea, though, if it makes the clamping action more positive.

Polymax (Bordon, Hants) offer a vast range of O-rings (use Viton quality for hydraulic fluid applications), with exact sizes listed, and available in quite small quantities.

[bobins]

I tried many different sized O rings to try and cure the leak from the pipes - none of them worked. A new pipe cured the problem. There were quite a few reports from garages back when the racks were first failing that blames corrosion of the pipes on subsequent leaks - I think that was a misdiagnosis. I read somewhere that Ford also consider their PS pipes single use on some of their cars (Fiesta's ?) due to the same issue.
When it's light tomorrow I'll go and check the old pipes I've got in the shed to see if there's any evidence on them of a compression fit into the pinion housing.

[white exec]

The whole arrangement is a bit suspect, and scruffily engineered: an aluminium pipe which can distort, a single O-ring not actively compressed by the clamp, and a potentially wobbly clamping device.

Interesting to compare that to all the standard Citroen hydraulic connections used elsewhere, which incorporate pressured olives or 'rubber' sleeves, and a threaded union. None of these tried and tested joints ever cause a problem, even though decades old.

It's a poor design, in my opinion, and deserves something much better. Choice is whether to attempt to make the most of it (eg twin and better O-rings and shims), or re-engineer it (eg by threading the bore).

Maybe, as you say, the design is so grim it doesn't really survive re-assembly, so new pipes are required. New pipes also bring with them new, fresh O-rings, of course.

[GiveMeABreak]

Annoyingly, without any regard for the design or the pinion - everything under the leak diagnostics for the steering mechanism is more or less replace the pipes or the steering rack! Culprits they blame are missing o rings, incorrect tightening, 'sealing fault' (now that's the cop out clause to me)....

[bobins]

I've just been out to The Shed Of Delights™ to find my old PS pipes. See photos....

How the pipe fits into the pinion housing:

PS pipe1 - own work

Pipe fully home:

PS pipe2 - own work

How far ring protrudes from housing i.e. not very far ! :

PS pipe4 - own work

Yoke that holds PS pipe in place. Note there's a chamfer on the yoke which means even less of a positive fit on the ring:

PS pipe5 - own work

The fitting of the yoke over the silver PS pipe is sufficiently slack to allow the silver pipe to move off alignment in its socket in the pinion housing. The silver pipe is not even close to being a tight fit in tis socket.